Electrical switch of the snap spring type



April 13, 1937 L. HOLM ELECTRICAL SWITCH OF THE SNAP SPRING TYPE Filed Dec. 15, 1954 byeg 38 22 W i2 E/A FQ/Mm Patented A r. 13, 1937 UNITED STATES ELECTRICAL SWITCH OF THE. SNAP SPRING TYPE Ludwig Holm, Stuttgart, Germany, assignor to Robert Bosch Aktiengesellschalt,

Germany Stuttgart,

Application December 13, 1934, Serial No. 757,407

- In Germany December 20, 1933 3 Claims.

The present invention relates to electric switch arrangements, more especially intended for refrigerators,"having a snap'spring the loading of which is influenced by altering the spacing of 5 the supporting points of the spring. In known arrangements of this kind the spring bearings are moved in the longitudinal direction of the spring, for example, by an adjusting screw, to vary the loading of the spring. These adjusting 10 devices are inconvenient, expensive and not always reliable,,because either a special guide for the displaceable spring bearing and an additional bearing for the adjusting screw, must be provided in the base-plate, or the spring bearing so as to be easily rotatable.

According to the invention, the arrangement is substantially simplified and improved by the spacing of the supporting points of the spring being no longer altered by displacement, but by a simple swivelling or angular movement-of one or both spring bearings. An arrangement is more especially preferable in which the spring bearing or bearings can be turned about an axis standin the spacing of the spring supports according to the invention. v

I is a thermostat which responds to the tem perature of the refrigerating chamber of a refrigerating plant or to the evaporator temperature. It consists of a spring bellows I2, loaded by a spring II, and filled with a liquid that greatly expands on variations in temperature. This bellows is enclosed in a casing I3, and connected by a pipe I4 with a container or casing (not shown) located in the refrigerating chamber or near the evaporator. The movements of the spring bellows I2 produced by alterations in temperature itself must be connected with the adjusting screw ing at right angles to the snap plane of the, spring.

Figure illustrates graphically the 'variation part of the switch casing. When the pin I5 presses sufiiciently strongly against the snap spring I6, the latter snaps into the other endposition, whereby the contacts I8, I9 are pressed upon each other, and thus the current is switched on. When the temperature of the refrigerator to be controlled sinks, the spring II compresses the bellows l2, and the pin I5 moves away from the snap spring I6, which now by the action of a spring 2i snaps back again into the original end-position shown in the drawing, whereby the two contacts I8, I9 are suddenly pulled apart. The construction of the contact-carrier II as a spring which is secured to the snap spring is especially advantageous for a rapid breaking of the contacts. w

The snap spring It is mounted with its ends in notches 22, which are-cut in bolts 23, and run parallel to the axis of the bolts. The ends of the snap spring bear with shoulders 24 against an edge 25 of the notch, whilst the extreme outer ends 33. of the spring project into conical recesses 26 in the bolts 23. This arrangement prevents a springing out of the spring. The bolts 23 are frictionally mounted in such a way in a base-plate 21, which will generally form a part of a casing enclosing the switch arrangement, that they can be turned by hand. To enable the bolts .to be turned simply with a screwdriver, grooves 28 are provided on the top end of the bolts. about their axis to a certain amount, the notches 22, and thus the edge 25 in each bolt, somewhat alter their position, and they are in fact, turned outwards (Figure 3). ever, the distance between the two bearing points in the two bolts 23 is increased and thus the loading of the spring I6 diminished. In Figure 5, 29 is the distance of the edge 25 from the axis 3ll--30 running at right angles to the line connecting the two bolts 23. If now the bolt 23 is so turned that the notch 22 assumes the position shown in broken lines, then the edge 25 has only a distance 3| from'the axis 3030, which is smaller by the amount 32 than in the first position of the bolt. turned in the same way, then the distance apart of the two bearing points (edges 25) of the spring I8 is increased by an amount that is twice as great as the amount 32. The spring I6 is thus now less strongly loaded than before.

I declare that what I claim is: 1. In a switch of the snap spring type, a snap spring, supports for said spring, operating means by the movement of which the spring quickly If thebolts 23 arerotated- In this way, how-- If the other bolt is snaps over from one position to the reverse position and vice versa, at least one of said supports being adjustable by rotation about an axis to vary I the loading of the spring, said axis being normal 5 to the plane of movement of the spring on snapp l. and a friction bearing for said rotatable support to secure by friction said support in every adjusted position. 2. In a switch of the snap spring type, a snap 10 spring, supports for said spring, operating means by the movement of.which the spring quickly snaps over from one position to the reverse position and vice versa, at least'one of saidsupports being adjustable by rotation about axis to livary the loading of thespring, said axis being normal to the plane of movement of thespring on 'snapp s. and a friction bearing forsaid rotatable support to secure by friction said support'in every adjusted position, said support consisting n of a rotatable member provided with'a recess extending longitudinally to and eocentrically of its snaps over from oneposltion to the reverse position and vice versa, at leastone of said supports being adjustable by rotation about an axis to vary the loading of the spring, said'axis being normal to the plane of movement of the spring on snap:

ping, a friction bearing for said rotatable support to secure by friction said support in every ad- Justed position, said support consisting of a rotatable member provided with a recess extending longitudinally to its axis and a tape ed opening leading from, the bottom of said recess, one end of said spring being provided with a shoulder and a projection, said shoulder resting on the bottom of the longitudinal recess and said projection extending into said opening of said member. I

LUDWIG HOLE. 

